1. Field of the Invention
The present invention relates to an electric-motor arrangement for a medical, in particular dental, hand piece. The electric-motor arrangement comprises an electric motor, in particular a small dental motor, that is to say an electric motor of compact design which is provided, in particular, for use in dental hand-held units. An electric-motor arrangement of this type is also called “dental motor” or “small dental motor” for short in the following text.
2. Related Technology
In particular, the invention relates to an electric-motor arrangement which is provided for being connected via a coupling to a medical, in particular to a dental hand piece and angular piece, also called “hand piece” for short in the following text, the hand piece being configured for receiving a rotatably mounted tool and, if the electric-motor arrangement is coupled to the hand piece as provided, it being possible for a torque which is generated by the electric-motor arrangement to be transmitted to the tool. A corresponding arrangement is known, for example, from DE 33 32 627 A1. Furthermore, it can be provided, in particular, that a supply hose is connected via a further coupling so as to lie opposite the hand piece, in relation to the electric-motor arrangement, which supply hose serves to supply the electric-motor arrangement or the hand piece and has, for example, medium lines, by which media such as air and/or water can be transported in order to form a spray. A power line and/or a light cable can also be arranged in the supply hose.
In an electric-motor arrangement of this type, it is desirable that the rotor of the electric motor vibrates as little as possible in the operating state. A long service life of the electric motor is also desirable. Therefore, mounting of the rotor as exactly as possible is usually aimed for without any alignment errors, in particular in the case of a fast-running dental motor.
The prior art has disclosed a corresponding electric-motor arrangement which has a motor housing, in which a bearing point for the rotor is formed integrally on that side which points towards the hand piece coupling; on the opposite, that is to say “rear” side, a further, that is to say “rear” bearing flange is centered in the motor housing. DE 10 2007 048 340 A1 discloses a corresponding electric-motor arrangement, in which the bearing points are integrated directly into the stator body. The components for these known electric-motor arrangements are in part difficult to produce. Moreover, there is the risk of alignment errors with respect to the ideal motor axis, and the bearing seat can be deformed by thermal effects resulting from the motor coil and/or a sterilization, with the result that, furthermore, ball-bearing outer rings of the bearings are deformed and a bearing setting by springs fails. Both lead to an increase in running noise, vibrations and premature wear or failure.
The invention provides a corresponding electric-motor arrangement which vibrates less during operation and in the process has a longer service life.
According to the invention, an electric-motor arrangement is provided for a medical, in particular dental, hand piece which has a motor housing and a rotor which is arranged in the motor housing so that it can be rotated about an axis via a first bearing and a second bearing; moreover, the electric-motor arrangement has a stator which is arranged around the rotor in relation to the axis. Furthermore, the electric-motor arrangement has a first bearing flange, in which the first bearing is received, and a second bearing flange, in which the second bearing is received. The first bearing flange is composed of metal and has a first circumferential face which is arranged so as to adjoin the motor housing directly. The second bearing flange is composed of metal and has a second circumferential face which is likewise arranged so as to adjoin the motor housing directly.
Running noise and vibrations can be reduced as a result. Moreover, premature wear and/or failure can be prevented.
The stator is advantageously arranged clamped in between the first bearing flange and the second bearing flange and is preferably centered radially in the motor housing in relation to the axis by the first bearing flange and the second bearing flange. Negative influencing of a bearing point by distortion and/or diameter change of the stator as a consequence of heating of a winding of the stator and/or distortion as a result of sterilization are/is therefore prevented or at least considerably reduced. This results in a particularly short tolerance chain for the bearing prestressing which is defined substantially by the length of the stator along the axis and the spacing of contact shoulders for ball bearings on a shaft of the rotor.
Furthermore, the electric-motor arrangement advantageously has a coupling element, in particular in the form of a coupling pin, for connection of the electric-motor arrangement to the medical hand piece, the coupling element preferably being configured in one piece with the motor housing.
It is known to feed a medium, for example water or air, to the hand piece through a medium line; as a result, for example, a spray can be formed for cooling a processing location. In particular, the medium is provided for an attachment tool which can be driven by the electric motor and which is attached to the hand piece, for example a rotary tool. According to the prior art, the medium is fed first of all by the supply hose, subsequently by the electric-motor arrangement and finally in the hand piece. To this end, a first medium-line section of the medium line can be arranged in the electric-motor arrangement, which first medium-line section extends parallel to the rotational axis, or axis for short, of the motor. A small tubular piece is usually provided for this purpose, which is arranged laid in a groove in the shell of the motor housing, outside a magnetic yoke of the electric motor. In an electric-motor arrangement which has a coupling pin for connection to the hand piece, it is known, furthermore, that a second medium-line section extends through the coupling pin. The second medium-line section therefore usually extends radially further to the inside in relation to the rotational axis than the first medium-line section. Furthermore, a medium-diverting means therefore has to be provided which connects the first medium-line section to the second medium-line section so as to guide medium, and in the process overcomes the radial difference. It is known from the prior art to provide a curved pipe for this purpose, or a medium-diverting means which is formed by depressions in end faces of the motor housing and the coupling. It is a problem here that complicated sealing points result.
According to a second aspect, furthermore, the invention is based on the object of specifying a corresponding electric-motor arrangement which is improved with respect to the seal in the region of the medium-diverting means.
According to the second aspect of the invention, an electric-motor arrangement for a medical, in particular dental, hand piece is provided, which electric-motor arrangement has a motor housing, and a rotor which is arranged in the motor housing so that it can be rotated about an axis via a bearing, the bearing being arranged so that it is gripped in a bearing flange. Furthermore, the electric-motor arrangement has a stator which is arranged around the rotor in relation to the axis. Furthermore, the electric-motor arrangement has a coupling pin which is arranged around the axis, and a first medium-line section for guiding a medium, the first medium-line section extending radially outside the rotor in relation to the axis. Furthermore, the electric-motor arrangement has a second medium-line section for further guiding the medium, which second medium-line section extends in the coupling pin, the second medium-line section being arranged radially closer to the axis than the first medium-line section, and a medium-diverting means for a connection which guides the medium between the first medium-line section and the second medium-line section. Here, the medium-diverting means is formed in the bearing flange.
As a result, the seal in the region of the medium-diverting means can be simplified.
Furthermore, the electric-motor arrangement advantageously has a sealing seat for sealing between the first medium-line section and the medium-diverting means or between the medium-diverting means and the second medium-line section, the sealing seat being formed in the bearing flange and/or in the stator and/or in the coupling pin, and an O-ring preferably being arranged in the sealing seat.
The first medium-line section is preferably integrated into the stator.
It can also advantageously be provided that the electric-motor arrangement has a flat seal which bears against the bearing flange for sealing between the first medium-line section and the medium-diverting means or between the medium-diverting means and the second medium-line section.
The bearing flange preferably has a radial hole, by which a part of the medium-diverting means is formed.
Furthermore, it is known from the prior art to provide a suck-back stop in a medium line, which suck-back stop prevents the medium, that is to say, for example, water, being sucked back or flowing back from the hand piece into the electric-motor arrangement and/or into the supply hose. It is known here to form the suck-back stop as a lip valve which is arranged in the interior of the motor housing so as to be protected in the axial direction. There is the problem here that the extent of the electric-motor arrangement has to be of longer design in the direction of the rotational axis as a result. As an alternative, it is known to implement the suck-back stop so that an O-ring is arranged at an outlet hole of the coupling pin, which O-ring opens only when the supply pressure is applied. However, there is the risk here that this O-ring is damaged or moved out of its provided position by cleaning and/or plug-in operations for connection to the hand piece.
According to the invention, a hose element made from elastic material is preferably arranged in the radial hole in the bearing flange. As a result, a suck-back stop can be formed which is arranged so that it is protected and in the process saves space. The elastic material can be, for example, rubber, silicone or Viton. Here, the hose element is preferably arranged in such a way that it bears against the inner wall of the hole and, without the action of external forces, closes a feed hole for the medium from the stator. The hose element can bear against the inner wall as a result of the internal stress; in the case of pressure from the inflow side, the hose element can rise up from the inner wall and can allow the medium to flow through in the direction of the hand piece. In the pressure less state, the hose element correspondingly bears against the inner wall and closes the feed hole, with the result that the medium cannot flow back to the stator and/or to the supply hose.
Here, furthermore, the electric-motor arrangement preferably has a pin element which is arranged in such a way that it protrudes into the hose element and seals the latter radially to the outside with respect to the medium. As a result, it can be achieved, in particular, that the hose element can rise up from the inner wall only to a limited extent. Moreover, the pin element can close the hole in the radial direction towards the circumference of the bearing flange.
As an alternative to the above-described solution, a lip valve could also be arranged in the medium-diverting means. Furthermore, there is the possibility to form the bearing flange integrally into the housing.
Furthermore, the invention relates to a dental instrument part which has an outer surface which is composed of titanium. The dental instrument part can be, for example, an electric-motor arrangement, in particular an electric-motor arrangement as is shown further above.
It is known from the prior art to use metallic materials for housings and sleeves of dental instruments (hand pieces and angular pieces, turbines) and also dental motors, for example stainless steel, brass, aluminum or titanium. In order to achieve an attractive external appearance and a certain wear protection, the surfaces of the steel and brass parts are finished by chemical or galvanic coatings (NiCr) or PVD coating (PVD: physical vapor deposition), as a result of which there is also protection with respect to preparation processes such as disinfection and/or thermal disinfection and sterilization. It is a problem here that PVD coatings require a comparatively high outlay on apparatus and are expensive. Moreover, the layer thicknesses which can be achieved here are only a few micrometers. Furthermore, there is the risk that the layers flake off from the base material in the case of insufficient pre-treatment (for example, cleaning) and/or mechanical stress (for example, deformation). A further disadvantage of these housing parts made from steel/brass is their comparatively high weight.
Housings and sleeves made from aluminum can be produced inexpensively and have a comparatively low mass. In this case, the surfaces can also be protected against wear by hard anodic layers. However, the surfaces do not permanently withstand the media used during preparation.
Housings and sleeves made from titanium have a comparatively low mass. Without additional coating, titanium withstands an attack by media and processes, as are usually used in the context of preparation. In addition, they have excellent biocompatibility, with the result that, in particular, no allergic reactions are to be feared, that is to say, in particular, neither in a patient nor in a user. However, the wear protection is limited; in addition, impairments of the external appearance occur as a result of signs of use such as scratches.
Particularly high requirements with respect to the wear and scratch resistance are made of the surface of a coupling pin of dental couplings (for example, MULTIflex, INTRAmatic). Here, very accurate fits are required which are also not supposed to and/or must not change during operation as a result of the attachment of hard objects, that is to say, for example, hand pieces and angular pieces or turbines. The attachment of corresponding exchangeable instruments takes place very frequently in the dental practice. In order to avoid wear and “scoring” of these highly loaded components, they are produced from steel and are tempered. Here, ergonomic disadvantages which are produced as a result of the higher weight are accepted. Titanium and its alloys generally have poor tribological properties. This is manifested in comparatively high coefficients of friction, adhesive wear and a pronounced tendency to “scoring”. Titanium and its alloys are therefore not used for coupling pins.
In dental instruments (hand pieces and angular pieces, turbines) and motors (pneumatic/electric motors), ergonomic aspects such as weight, but also robust and scratch-resistant surfaces with a satisfactory resistance to the media used during preparation (hot steam; alkaline and acidic cleaners; hydrocarbon compounds, inter alia) and processes (temperature, pressure, vacuum) and satisfactory haptics are decisive.
According to a further aspect, the invention is therefore based on the object of specifying a medical instrument part, in particular a dental instrument part, which is not damaged by preparation and in the process is improved ergonomically.
According to this aspect of the invention, a medical instrument part, in particular a dental instrument part, is provided which has an outer surface which is composed of titanium. The dental instrument part can be, for example, an electric-motor arrangement, as is shown further above. Here, the surface is tempered by a hardening process.
This achieves a situation where the medical instrument part can be configured with particularly low weight and can therefore be of ergonomically particularly advantageous design. Moreover, it is particularly scratch-resistant and abrasion-resistant and has a particularly low cold sweat tendency. Furthermore, the medical instrument part is particularly resistant to conventional preparation methods and processes such as thermal disinfection or hot-steam sterilization in autoclaves.
Here, the surface is advantageously tempered based on a thermo chemical diffusion process, the thermo chemical diffusion process preferably being what is known as “oxygen diffusion hardening.”
The dental instrument part particularly preferably has a coupling pin which is provided for connection to a further dental instrument part, for example to a hand piece and angular piece, the outer surface being an outer surface of the coupling pin.
Dental instruments, in particular pneumatic/electric motors contain components which have to be maintained regularly and which have to be readily accessible for exchanging, for example in the case of a repair, such as a halogen lamp or an LED.
In order to avoid light scatter and in order to protect the electric contacts, halogen lamps and their connection plugs are arranged in the instrument so that they are protected by means of sleeves or protective caps or the like.
Here, it is known, for example, to fasten a sleeve to a motor housing by means of a threaded device. There is the problem here that thin, short threaded rings are deformed by comparatively low forces, as already have to be applied, for example, in order to overcome the thread friction, and therefore adhere all the more to the thread. It is only possible to release the threaded connection with a pressure which is distributed more or less uniformly over the entire circumference. Two fingers are usually used for the release, it being comparatively difficult to produce a correspondingly uniform pressure with two fingers. Furthermore, dirt can be deposited in the thread in practice by incorrect cleaning and care, which can lead to even considerably greater moments being required for the release. The “deformed sleeve and release problems” effect is therefore reinforced further.
Furthermore, it is known from the prior art that sleeves or protective caps are clipped on and are held via sprung pins/balls. In this case, the sleeves can also be pulled off in the case of moderate contamination. However, the ball/pin with cylinder spring design requires a relatively large amount of radial installation space, which opposes a compact overall embodiment. In the case of penetration of dirt, deposits and the like on account of insufficient care in the movement space of the ball, pulling the protective sleeve off is also made difficult in this solution.
Furthermore, it is known to clip on a sleeve or protective cap with an undercut, the sleeve being pressed or deformed for release. Although clipping a round sleeve onto an oval or flattened seat on the basic body is an elegant solution, above all, for thin, short sleeves and protective caps, this release of the sleeve is made difficult or prevented by deformation and adaptation to the oval shape of the basic body as a result of accumulation of contaminants or deposits in the movement space for the sleeve during release; Here, the undercut of the sleeve rises up out of the notch on the basic body.
The invention is therefore based, furthermore, on the object of specifying a dental instrument which has an improved holding mechanism for a sleeve or protective cap or the like.
According to this aspect of the invention, a dental instrument is provided which has a housing and an instrument part which is arranged removably on the housing. Here, the instrument part has an annular region which is arranged so as to reach around an outer circumferential face of the housing. A depression is arranged on the outer circumferential face, in which depression at least one preferably spherical, elastic holding part is received, an undercut being arranged in the annular region, into which undercut the elastic holding part engages.
In this way, a holding mechanism is provided which can be opened and closed easily and reliably, even in the case of relatively powerful pressing together with two fingers and under the influence of deposits and contaminants as a result of insufficient care in the gap between the instrument part and the housing. For example, the holding mechanism is suitable particularly satisfactorily for an instrument part in the form of a thin-walled sleeve or protective cap which is arranged, for example, on an electric-motor arrangement.
The depression is preferably configured in such a way that the elastic holding part only partially fills the volume which is defined by the depression. In this way, a “deformation space” is formed by the depression, which deformation space is available for deformation of the elastic holding part while the instrument part is being pulled off or attached.